It is conventionally known, as described in Patent Literature 1 (Japanese Unexamined Patent Application Publication No. 2013-6495) for example, that a conveying traveling body used in an automobile assembly line, etc., so as to convey a large workpiece is composed of a central main wagon mainly used for workpiece support and the working floor with respect to left and right both side portions of the workpiece and a front and a rear two auxiliary wagons mainly used for the working floor with respect to front and rear both end portions of the workpiece. In this kind of conveyance device, it is also known from the above Patent Literature 1 that the central main wagon and the front and rear two auxiliary wagons are configured to be coupled by the wagon-to-wagon coupling means and handled as a single conveying traveling body to convey one workpiece by means of this plurality of front to rear wagons. However, in the configuration described in this Patent Literature 1, the wagon-to-wagon coupling means are provided in a normally coupled state to only one of left and right both side portions of the conveying traveling body, which side portion becomes the inner side in a curving direction of the horizontal turn path section in the travel path.